1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Copyright (c) 2013, Google Inc.
4 */
5
6 #ifndef USE_HOSTCC
7 #include <common.h>
8 #include <fdtdec.h>
9 #include <asm/types.h>
10 #include <asm/byteorder.h>
11 #include <linux/errno.h>
12 #include <asm/types.h>
13 #include <asm/unaligned.h>
14 #else
15 #include "fdt_host.h"
16 #include "mkimage.h"
17 #include <fdt_support.h>
18 #endif
19 #include <u-boot/rsa.h>
20 #include <u-boot/rsa-mod-exp.h>
21
22 #define UINT64_MULT32(v, multby) (((uint64_t)(v)) * ((uint32_t)(multby)))
23
24 #define get_unaligned_be32(a) fdt32_to_cpu(*(uint32_t *)a)
25 #define put_unaligned_be32(a, b) (*(uint32_t *)(b) = cpu_to_fdt32(a))
26
27 /* Default public exponent for backward compatibility */
28 #define RSA_DEFAULT_PUBEXP 65537
29
30 /**
31 * subtract_modulus() - subtract modulus from the given value
32 *
33 * @key: Key containing modulus to subtract
34 * @num: Number to subtract modulus from, as little endian word array
35 */
subtract_modulus(const struct rsa_public_key * key,uint32_t num[])36 static void subtract_modulus(const struct rsa_public_key *key, uint32_t num[])
37 {
38 int64_t acc = 0;
39 uint i;
40
41 for (i = 0; i < key->len; i++) {
42 acc += (uint64_t)num[i] - key->modulus[i];
43 num[i] = (uint32_t)acc;
44 acc >>= 32;
45 }
46 }
47
48 /**
49 * greater_equal_modulus() - check if a value is >= modulus
50 *
51 * @key: Key containing modulus to check
52 * @num: Number to check against modulus, as little endian word array
53 * @return 0 if num < modulus, 1 if num >= modulus
54 */
greater_equal_modulus(const struct rsa_public_key * key,uint32_t num[])55 static int greater_equal_modulus(const struct rsa_public_key *key,
56 uint32_t num[])
57 {
58 int i;
59
60 for (i = (int)key->len - 1; i >= 0; i--) {
61 if (num[i] < key->modulus[i])
62 return 0;
63 if (num[i] > key->modulus[i])
64 return 1;
65 }
66
67 return 1; /* equal */
68 }
69
70 /**
71 * montgomery_mul_add_step() - Perform montgomery multiply-add step
72 *
73 * Operation: montgomery result[] += a * b[] / n0inv % modulus
74 *
75 * @key: RSA key
76 * @result: Place to put result, as little endian word array
77 * @a: Multiplier
78 * @b: Multiplicand, as little endian word array
79 */
montgomery_mul_add_step(const struct rsa_public_key * key,uint32_t result[],const uint32_t a,const uint32_t b[])80 static void montgomery_mul_add_step(const struct rsa_public_key *key,
81 uint32_t result[], const uint32_t a, const uint32_t b[])
82 {
83 uint64_t acc_a, acc_b;
84 uint32_t d0;
85 uint i;
86
87 acc_a = (uint64_t)a * b[0] + result[0];
88 d0 = (uint32_t)acc_a * key->n0inv;
89 acc_b = (uint64_t)d0 * key->modulus[0] + (uint32_t)acc_a;
90 for (i = 1; i < key->len; i++) {
91 acc_a = (acc_a >> 32) + (uint64_t)a * b[i] + result[i];
92 acc_b = (acc_b >> 32) + (uint64_t)d0 * key->modulus[i] +
93 (uint32_t)acc_a;
94 result[i - 1] = (uint32_t)acc_b;
95 }
96
97 acc_a = (acc_a >> 32) + (acc_b >> 32);
98
99 result[i - 1] = (uint32_t)acc_a;
100
101 if (acc_a >> 32)
102 subtract_modulus(key, result);
103 }
104
105 /**
106 * montgomery_mul() - Perform montgomery mutitply
107 *
108 * Operation: montgomery result[] = a[] * b[] / n0inv % modulus
109 *
110 * @key: RSA key
111 * @result: Place to put result, as little endian word array
112 * @a: Multiplier, as little endian word array
113 * @b: Multiplicand, as little endian word array
114 */
montgomery_mul(const struct rsa_public_key * key,uint32_t result[],uint32_t a[],const uint32_t b[])115 static void montgomery_mul(const struct rsa_public_key *key,
116 uint32_t result[], uint32_t a[], const uint32_t b[])
117 {
118 uint i;
119
120 for (i = 0; i < key->len; ++i)
121 result[i] = 0;
122 for (i = 0; i < key->len; ++i)
123 montgomery_mul_add_step(key, result, a[i], b);
124 }
125
126 /**
127 * num_pub_exponent_bits() - Number of bits in the public exponent
128 *
129 * @key: RSA key
130 * @num_bits: Storage for the number of public exponent bits
131 */
num_public_exponent_bits(const struct rsa_public_key * key,int * num_bits)132 static int num_public_exponent_bits(const struct rsa_public_key *key,
133 int *num_bits)
134 {
135 uint64_t exponent;
136 int exponent_bits;
137 const uint max_bits = (sizeof(exponent) * 8);
138
139 exponent = key->exponent;
140 exponent_bits = 0;
141
142 if (!exponent) {
143 *num_bits = exponent_bits;
144 return 0;
145 }
146
147 for (exponent_bits = 1; exponent_bits < max_bits + 1; ++exponent_bits)
148 if (!(exponent >>= 1)) {
149 *num_bits = exponent_bits;
150 return 0;
151 }
152
153 return -EINVAL;
154 }
155
156 /**
157 * is_public_exponent_bit_set() - Check if a bit in the public exponent is set
158 *
159 * @key: RSA key
160 * @pos: The bit position to check
161 */
is_public_exponent_bit_set(const struct rsa_public_key * key,int pos)162 static int is_public_exponent_bit_set(const struct rsa_public_key *key,
163 int pos)
164 {
165 return key->exponent & (1ULL << pos);
166 }
167
168 /**
169 * pow_mod() - in-place public exponentiation
170 *
171 * @key: RSA key
172 * @inout: Big-endian word array containing value and result
173 */
pow_mod(const struct rsa_public_key * key,uint32_t * inout)174 static int pow_mod(const struct rsa_public_key *key, uint32_t *inout)
175 {
176 uint32_t *result, *ptr;
177 uint i;
178 int j, k;
179
180 /* Sanity check for stack size - key->len is in 32-bit words */
181 if (key->len > RSA_MAX_KEY_BITS / 32) {
182 debug("RSA key words %u exceeds maximum %d\n", key->len,
183 RSA_MAX_KEY_BITS / 32);
184 return -EINVAL;
185 }
186
187 uint32_t val[key->len], acc[key->len], tmp[key->len];
188 uint32_t a_scaled[key->len];
189 result = tmp; /* Re-use location. */
190
191 /* Convert from big endian byte array to little endian word array. */
192 for (i = 0, ptr = inout + key->len - 1; i < key->len; i++, ptr--)
193 val[i] = get_unaligned_be32(ptr);
194
195 if (0 != num_public_exponent_bits(key, &k))
196 return -EINVAL;
197
198 if (k < 2) {
199 debug("Public exponent is too short (%d bits, minimum 2)\n",
200 k);
201 return -EINVAL;
202 }
203
204 if (!is_public_exponent_bit_set(key, 0)) {
205 debug("LSB of RSA public exponent must be set.\n");
206 return -EINVAL;
207 }
208
209 /* the bit at e[k-1] is 1 by definition, so start with: C := M */
210 montgomery_mul(key, acc, val, key->rr); /* acc = a * RR / R mod n */
211 /* retain scaled version for intermediate use */
212 memcpy(a_scaled, acc, key->len * sizeof(a_scaled[0]));
213
214 for (j = k - 2; j > 0; --j) {
215 montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod n */
216
217 if (is_public_exponent_bit_set(key, j)) {
218 /* acc = tmp * val / R mod n */
219 montgomery_mul(key, acc, tmp, a_scaled);
220 } else {
221 /* e[j] == 0, copy tmp back to acc for next operation */
222 memcpy(acc, tmp, key->len * sizeof(acc[0]));
223 }
224 }
225
226 /* the bit at e[0] is always 1 */
227 montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod n */
228 montgomery_mul(key, acc, tmp, val); /* acc = tmp * a / R mod M */
229 memcpy(result, acc, key->len * sizeof(result[0]));
230
231 /* Make sure result < mod; result is at most 1x mod too large. */
232 if (greater_equal_modulus(key, result))
233 subtract_modulus(key, result);
234
235 /* Convert to bigendian byte array */
236 for (i = key->len - 1, ptr = inout; (int)i >= 0; i--, ptr++)
237 put_unaligned_be32(result[i], ptr);
238 return 0;
239 }
240
rsa_convert_big_endian(uint32_t * dst,const uint32_t * src,int len)241 static void rsa_convert_big_endian(uint32_t *dst, const uint32_t *src, int len)
242 {
243 int i;
244
245 for (i = 0; i < len; i++)
246 dst[i] = fdt32_to_cpu(src[len - 1 - i]);
247 }
248
rsa_mod_exp_sw(const uint8_t * sig,uint32_t sig_len,struct key_prop * prop,uint8_t * out)249 int rsa_mod_exp_sw(const uint8_t *sig, uint32_t sig_len,
250 struct key_prop *prop, uint8_t *out)
251 {
252 struct rsa_public_key key;
253 int ret;
254
255 if (!prop) {
256 debug("%s: Skipping invalid prop", __func__);
257 return -EBADF;
258 }
259 key.n0inv = prop->n0inv;
260 key.len = prop->num_bits;
261
262 if (!prop->public_exponent)
263 key.exponent = RSA_DEFAULT_PUBEXP;
264 else
265 key.exponent =
266 fdt64_to_cpu(*((uint64_t *)(prop->public_exponent)));
267
268 if (!key.len || !prop->modulus || !prop->rr) {
269 debug("%s: Missing RSA key info", __func__);
270 return -EFAULT;
271 }
272
273 /* Sanity check for stack size */
274 if (key.len > RSA_MAX_KEY_BITS || key.len < RSA_MIN_KEY_BITS) {
275 debug("RSA key bits %u outside allowed range %d..%d\n",
276 key.len, RSA_MIN_KEY_BITS, RSA_MAX_KEY_BITS);
277 return -EFAULT;
278 }
279 key.len /= sizeof(uint32_t) * 8;
280 uint32_t key1[key.len], key2[key.len];
281
282 key.modulus = key1;
283 key.rr = key2;
284 rsa_convert_big_endian(key.modulus, (uint32_t *)prop->modulus, key.len);
285 rsa_convert_big_endian(key.rr, (uint32_t *)prop->rr, key.len);
286 if (!key.modulus || !key.rr) {
287 debug("%s: Out of memory", __func__);
288 return -ENOMEM;
289 }
290
291 uint32_t buf[sig_len / sizeof(uint32_t)];
292
293 memcpy(buf, sig, sig_len);
294
295 ret = pow_mod(&key, buf);
296 if (ret)
297 return ret;
298
299 memcpy(out, buf, sig_len);
300
301 return 0;
302 }
303
304 #if defined(CONFIG_CMD_ZYNQ_RSA)
305 /**
306 * zynq_pow_mod - in-place public exponentiation
307 *
308 * @keyptr: RSA key
309 * @inout: Big-endian word array containing value and result
310 * @return 0 on successful calculation, otherwise failure error code
311 *
312 * FIXME: Use pow_mod() instead of zynq_pow_mod()
313 * pow_mod calculation required for zynq is bit different from
314 * pw_mod above here, hence defined zynq specific routine.
315 */
zynq_pow_mod(u32 * keyptr,u32 * inout)316 int zynq_pow_mod(u32 *keyptr, u32 *inout)
317 {
318 u32 *result, *ptr;
319 uint i;
320 struct rsa_public_key *key;
321 u32 val[RSA2048_BYTES], acc[RSA2048_BYTES], tmp[RSA2048_BYTES];
322
323 key = (struct rsa_public_key *)keyptr;
324
325 /* Sanity check for stack size - key->len is in 32-bit words */
326 if (key->len > RSA_MAX_KEY_BITS / 32) {
327 debug("RSA key words %u exceeds maximum %d\n", key->len,
328 RSA_MAX_KEY_BITS / 32);
329 return -EINVAL;
330 }
331
332 result = tmp; /* Re-use location. */
333
334 for (i = 0, ptr = inout; i < key->len; i++, ptr++)
335 val[i] = *(ptr);
336
337 montgomery_mul(key, acc, val, key->rr); /* axx = a * RR / R mod M */
338 for (i = 0; i < 16; i += 2) {
339 montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod M */
340 montgomery_mul(key, acc, tmp, tmp); /* acc = tmp^2 / R mod M */
341 }
342 montgomery_mul(key, result, acc, val); /* result = XX * a / R mod M */
343
344 /* Make sure result < mod; result is at most 1x mod too large. */
345 if (greater_equal_modulus(key, result))
346 subtract_modulus(key, result);
347
348 for (i = 0, ptr = inout; i < key->len; i++, ptr++)
349 *ptr = result[i];
350
351 return 0;
352 }
353 #endif
354